chore: cleanup for push to main

- Remove CLAUDE.md, TODO.md (dev-only task trackers)
- Remove umutray.service (unused systemd unit)
- Remove .vscode/settings.json (stale Makefile ref)
- Add src/theme.rs (shared palette/styling module)
- Update .gitignore: exclude .vscode/, packaging build artifacts
- Fix README: add gui command, correct service description
- Delete ~1.3GB packaging build artifacts from working tree

Code changes from prior session (already committed locally):
- Tray icon launches alongside GUI, close dialog with minimize-to-tray
- Theme module extraction, button shadow fixes, UI polish
- Game detection filtering, prettify_game_name, Battle.net fix

.gitignore

@@ -1 +1,8 @@
 /target
+.vscode/
+
+# Packaging build artifacts
+packaging/pkg/
+packaging/src/
+packaging/umutray/
+packaging/*.pkg.tar.zst